How to parse complex JSON array in Java?

How to parse complex JSON array in Java?

Introduction:
JSON (JavaScript Object Notation) has become one of the most commonly used data exchange formats in modern web applications. In Java development, we often need to parse and process complex JSON data structures. This article will introduce how to use the JSON library in Java to parse complex JSON arrays, and demonstrate the specific steps through code examples.

This article will be divided into the following parts:

1. Introducing the required dependency libraries
2. Loading JSON data
3. Parsing and processing JSON arrays
4. Sample code
5. Introduce the required dependent libraries
   First, before using the JSON library for JSON parsing in a Java project, you need to add the relevant dependent libraries to the project's build file . Here, we will use the commonly used JSON library - Jackson. In the Maven project, you can add the following dependencies in the pom.xml file:

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.12.5</version>
</dependency>

2. Loading JSON data
   Before you start parsing the JSON array, you first need to load the JSON data. JSON data can be read from files, network interfaces or strings. In this article, we will use an example string containing a complex JSON array:

String json = "[{"id":"1","name":"Alice","age":25},{"id":"2","name":"Bob","age":30}]";

3. Parsing and processing JSON array
   Next, we will use the Jackson library to parse and process JSON array. The Jackson library provides a convenient set of APIs to parse JSON data. The following are the general steps for parsing a JSON array:

a. Create an ObjectMapper object:
ObjectMapper is the core class of the Jackson library and is used to convert JSON strings into Java objects. ObjectMapper objects can be created in the following ways:

ObjectMapper objectMapper = new ObjectMapper();

b. Create a Java class to map JSON data:
In order to facilitate subsequent operations, we can create a Java class to map the structure of JSON data. In this example, we will create a class called Person that has id, name, and age properties:

public class Person {
    private String id;
    private String name;
    private int age;
    
    public String getId() {
        return id;
    }
    
    public void setId(String id) {
        this.id = id;
    }
    
    public String getName() {
        return name;
    }
    
    public void setName(String name) {
        this.name = name;
    }
    
    public int getAge() {
        return age;
    }
    
    public void setAge(int age) {
        this.age = age;
    }
}

c. Parse the JSON array:
Now, we can use the ObjectMapper object to convert the JSON The data is parsed as an array of Java objects. JSON strings can be converted into Java objects using the readValue() method. The following is a sample code to parse a JSON array:

List<Person> persons = objectMapper.readValue(json, new TypeReference<List<Person>>(){});

4. Sample code
   The following is a complete sample code that demonstrates how to parse a complex JSON array in Java:

import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;

import java.util.List;

public class JsonArrayParser {
    public static void main(String[] args) {
        // JSON数据示例
        String json = "[{"id":"1","name":"Alice","age":25},{"id":"2","name":"Bob","age":30}]";
        
        // 创建ObjectMapper对象
        ObjectMapper objectMapper = new ObjectMapper();
        
        try {
            // 解析JSON数组
            List<Person> persons = objectMapper.readValue(json, new TypeReference<List<Person>>(){});
            
            // 遍历解析结果
            for (Person person : persons) {
                System.out.println("ID: " + person.getId());
                System.out.println("Name: " + person.getName());
                System.out.println("Age: " + person.getAge());
                System.out.println();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

class Person {
    private String id;
    private String name;
    private int age;
    
    // getter and setter methods
}

Summary:
This article introduces how to parse complex JSON arrays in Java. By using the Jackson library, we can easily parse JSON data into Java objects and perform further processing and manipulation on them. I hope this article can help you better process and use JSON data.

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